The fullback proved the matchwinner against Fiorentina on Saturday, though has struggled for form this season.
Pioli said: "It happens to everyone that we get criticised when we haven't won in many games.
"He has the qualities to always play great matches. Regarding positions on the pitch: our players are very good at occupying the right positions.
"Theo went to the middle of the pitch to take the penalty and provide a great assist for (Luka) Jovic."